1. Field of the Invention
This invention relates broadly to the field of metering applicator apparatus and, more particularly, to a constant displacement pump arrangement for an applicator for discharging carefully controlled amounts of fluid.
2. Description of the Prior Art
There are fields of endeavor that require the use of a carefully controlled amount of fluid that must be discharged from an applicator along a predetermined path. More specifically, for instance, in a high-speed can end processing machine, 400 or more can ends per minute are moved individually past a station where a controlled amount of fluid or compound is administered to each can end at a particular location on the can end.
The compound administered to the can end is either a hot melt thermoplastic or a rubber base material such as a latex which is administered in very limited quantities, at very high speeds and in such a way that, at least in one form of use, it will form a bead around the outer edge of the can end. The bead should not overlap excessively and should have a degree of integrity as applied to the rotating can end so as not to be spun or flung outward excessively from the locations where it is applied.
In order to administer the very limited quantities of fluid or compound to the can end in the very limited amount of time that the rotating can end is aligned with the nozzle, requires very careful control of the amount of fluid dispensed and requires an instantaneous start and stop of the dispensing cycle.
Heretofore, very complicated and expensive controls and pump arrangements have been provided for maintaining the source of compound to the applicator or nozzle within the requisite controlled limits. Because the amounts of fluid or compound to be discharged are so relatively minuscule, it has been difficult to provide the proper degree of control of the amounts of compound to the applicator resulting in less than totally efficient functioning of the applicator. Since the prior art devices are rather expensive and complicated, they frequently become jammed or their accuracy drifts and the precise amounts necessary are no longer obtainable.